Method of spectrally sensitizing photographic silver halide emulsions

ABSTRACT

LIGHT SENSITIVE SILIVER HALIDE IS SPECTRALLY SENSITIZED BY DISPERSING A SUBSTANTIALLY WATER-INSOLUBLE PHOTOGRAPHIC SPECTRAL SENSITIZING DYE INTO A WATER-SOLUBLE ORGAINC LIQUID WITHOUT DISSOLVING THE DYE, AND INCORPORATING THE DISPERSION INOT A LIQUID PHOTOGRAPHIC SILVER HALIDE EMULSION. NOVEL DISPERSIONS OF DYES ARE ALSO PROVIDED.

United States Patent "ice 180,194 Int. Cl. G03c 1/16', 1/18, 1/20 US.Cl. 96-130 13 Claims ABSTRACT OF THE DISCLOSURE Light sensitive silverhalide is spectrally sensitized by dispersing a substantiallywater-insoluble photograph c spectral sensitizing dye into awater-soluble organic hquid without dissolving the dye, andincorporating the dispersion into a liquid photographic silver halideemulsion. Novel dispersions of dyes are also provided.

This invention relates to novel photographic processes and moreparticularly to novel processes for spectrally sensitizing photographicsilver halide emulsions. It also relates to novel photographic materialsand processes.

The conventional method of sensitizing light sensitive silver halideconsists of dissolving the sensitizing dye in an appropriate organicsolvent, such as methyl alcohol, ethyl alcohol, acetone, etc., andadding the resulting solution to a liquid photographic silver halideemulsion. While this general method has provided a commercially feasiblemeans for incorporating sensitizing dyes into silver halide emulsions,it still requires considerable care and extra manipulative steps inadjusting the volume of solvent to quantities that are compatible withthe particular emulsion and still produce the desired results. Also, itis well known that excessive solvent engenders disadvantageous diffusionor wandering of the sensitizing dyes in the emulsions.

It is, accordingly, an object of this invention to provide a new methodfor spectrally sensitizing light sensitive silver halide.

Another object of this invention is to provide novel dispersions ofspectral sensitizing dye.

Other objects of this invention will be apparent from this disclosureand the appended claims.

'In accordance with one embodiment of this invention, a process isprovided for spectrally sensitizing photographic silver halide whichcomprises: dispersing a substantially water-insoluble photographicspectral sensitizing dye into a water-soluble organic liquid withoutdissolving the dye; and, incorporating the dispersion into a liquidphotographic silver halide emulsion.

In accordance with another embodiment of this invention, novel dyedispersions are provided which comprise undissolved particles of aphotographic spectral sensitizing dye in a water-soluble organic liquid.

In still another embodiment of this invention, novel compositions areprovided which comprise a hydrophilic colloid containing undissolvedparticles of photographic spectral sensitizing dye in a water-solubleorganic liquid in which said dye is substantially insoluble. Suchcomposition can be either liquid or solid; either form is useful forspectrally sensitizing liquid photographic silver halide emulsions.

The dye dispersions of the invention are especially useful in coatingprocesses which require low amounts of organic solvent. The dyedispersions are stable and can be conveniently stored or transported.

The compositions of dye in organic liquid can be prepared in anyconvenient manner. Ball milling the dye and organic liquid gives highlysatisfactory results. Ad-

3,676,147 Patented July 11, 1972 vantageously, the liquid contains dyeparticles which have an average diameter of up to about 1.0 micron.

Organic liquids which can be used in the practice of this invention arewater-soluble materials, and are liquids below about 30 C. Organicliquids can be used which are not solvents for the photographicsensitizing dye that is being used. Such organic liquids are oilymaterials. They should not have any adverse effects on the photographicemulsion in which they are incorporated. Also useful are organic liquidswhich are solvents for the dye. Such organic liquids, e.g., methanol,ethanol or isopropanol are used at sufficiently low levels, compared tothe quantity of dye, that only very small amounts of dye are dissolved.Both types of liquids function to separate, or prevent agglomeration ofthe dye particles. Such separation is essential to eflective spectralsensitization.

Typical organic liquids that are not dye solvents which can be used inthe invention are represented by the following formula:

wherein R represents a hydrogen atom or a lower alkyl group containing 1to 4 carbon atoms, e.g., methyl, ethyl, butyl, etc.; R represents ahydrogen atom or a methyl group; R represents a hydrogen atom, an alkylgroup containing from 1 to 3 carbon atoms, e.g., methyl, ethyl, propylor isopropyl, a hydroxymethyl group or an acetoxymethyl group; and Rrepresents a divalent alkylene group containing from 1 to 4 carbonatoms, e.g., -CH a)s 2)2, 2)3 0T and wherein the sum of the carbon atomsin said R R and R is a positive integer of from 1 to 4. Typical usefulliquids embraced by Formula I above include glycerol, monoacetin,ethylene glycol, methylglycol, (monomethyl ether of ethylene glycol),ethyl glycol ether, propyl glycol ether, butyl glycol ether,1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol,2,3-butylene glycol, isobutylene glycol (Z-methyl-1,2-propanediol),2-methyl-2, 3-butanediol, 3-methyl-l,3-butanediol, 1,2-pentanediol, l,4-pentanediol, 2,3-pentanediol, 1,5-pentanediol, etc. Glycerol andmethylglycol are the preferred solvents herein.

Also useful in the practice of this invention are organic liquids whichare solvents for spectral sensitizing dyes. Such liquids are used insufiiciently small amounts, relative to the quantity of spectralsensitizing dye, that no substantial amounts of dye are dissolved.Preferably, such liquids have a dissolving power for the dyes of lessthan 10 grams of dye per liter of solvent at 20 C. Useful organicliquids of this class include alcohols having from 1 to 4 carbon atoms,such as methanol, ethanol, n-propanol, iso-propanol, n-butanol,iso-butanol or tert butanol; acetone; and, dimethylformamide. Suchsolvents provide less tacky dye dispersions than similar dispersionsmade with relatively high boiling organic liquids.

Especially good results are obtained with a mixture of one or moreorganic liquids which are non-solvents for the dye, together with one ormore organic liquids which are solvents for the dye. A typical usefulsolvent mixture of this type is a mixture of methanol (which is asolvent for most sensitizing dyes) together with glycerol (which is anon-solvent for most sensitizing dyes). Particularly good results areobtained with an organic liquid mixture comprising about to 95 parts byweight solvent (e.g., methanol) and 20 to 5 parts by weight of anon-solvent liquid (e.g., glycerol) and preferably about parts by Weightsolvent and 10 parts by weight non-solvent.

The spectral sensitizing dye is dispersed in the organic liquid withoutdissolving the dye. As used herein, the term without dissolving the dyemeans that no substantial amount of dye is dissolved. Preferably, lessthan about by weight of the total dye mixed with the liquid isdissolved. Essentially no dye is dissolved when the dye is insoluble inthe organic liquid. When the organic liquid is one which will dissolvethe dye, the solvent is used in such small concentrations relative tothe total amount of dye that no substantial amount of dye is dissolved.Typical solutions of sensitizing dye in organic solvent, e.g., methanol,contain about 1 to 3 grams dye per liter of solvent. In accordance withthis invention, preferably about 5 to 20 cc. of solvent are used pergram of dye.

This invention can be practiced with any of the photographic spectralsensitizing dyes. The invention is especially useful with the dyes thatare substantially insoluble in aqueous solutions, e.g., dyes which havea solubility in water (at 20 C.) of less than about 1%. Typical dyeswhich can be used in the practice of this invention are described in thefollowing patents, the disclosure of which are incorporated herein byreference.

Zeh et al. U.S. Pat. No. 2,068,047, issued 1/19/37 Brooker U.S. Pat. No.2,078,233, issued 4/27/37 Koslowsky U.S. Pat. No. 2,107,379, issued 2/8/ 38 Mees U.S. Pat. No. 2,158,883, issued 5/16/39 Brooker et al. U.S.Pat. No. 2,161,331, issued 6 /6/39 Brooker U.S. Pat. No. 2,170,807,issued 8/29/39 Brooker U.S. Pat. No. 2,177,402, issued 24/ 39 BrookerU.S. Pat. No. 2,177,403, issued 10/24/39 Carroll et a1. U.S. Pat. No.2,177,635, issued 10/31/39 Carroll U.S. Pat. No. 2,206,076, issued7/2/40 Brooker U.S. Pat. No. 2,211,762, issued 8/20/40 Brooker et al.U.S. Pat. No. 2,213,238, issued 9/3/40 Brooker U.S. Pat. No. 2,307,916,issued 1/ 12/43 Brooker et al. US. Pat. No. 2,313,922, issued 3/16/43Schneider U.S. Pat. No. 2,374,505, issued 4/24/43 Falleson et al. U.S.Pat. No. 2,378,917, issued 6/26/45 Brooker U.S. Pat. No. 2,454,629,issued 11/23/48 Thompson U.S. Pat. No. 2,535,993, issued 12/26/50Carroll et al. U.S. Pat. No. 2,950,196, issued 8/23/60 Brooker et al.U.S. Pat. No. 2,955,939, issued 10/11/60 Jones U.S. Pat. No. 2,961,318,issued 11/22/60 Brooker et al. U.S. Pat. No. 2,194,805, issued 7/13/65Tabor et al. U.S. Pat. No. 3,335,010, issued 8/8/67 Brooker et al. U.S.Reissue No. 24,292, reissued 3/ 19/57 1.6., British Pat. No. 434,235,accepted 8/28/ 35 The following table lists a number of cyanine dyesthat are used in the examples hereinafter to illustrate the invention.

TABLE 1 Dye No.: Compound I 1'-ethyl-2-methylthia-4'-cyanine iodide II3,3'-diethyl-9-methylselenacarbocyanine bromide III1,1'-diethyl-2,2'-cyanine iodide IV 3-ethyl-5-[ 3-ethyl-2(3H)-benzothiazolylidene isopropylidene] -2-thjo-2,4-oxazolidinedione V9-ethyl-3,3'-di(B-methoxyethyl)-5,5-

diphenyloxacarbocyanine iodide VIAnhydro-5,5,6,6-tetrachloro-1,1-diethyl-3,3'-di(3-sulfobutyl)benzimidazolocarbocyanine hydroxide VII 5(3-ethyl-2(3H) -naphtho[2,1]oxazolylidene )ethylene]-3-n-heptyl-1-phenyl-2- thiohydantoin VIII5-(3-ethy1-2(3H)-benzoxazolylidene)-3- phenylrhodanine 1XAnhydro-5,5'-dichloro-3,9-diethyl-3-(3- sulfobutyl)thiacarbocyaninehydroxide lylidene) isopropylene] -1,3-di-(flmethoxyethyl)barbituricacid TABLE IContinuecl Dye No.: Compound XI3-ethyl-5-[1-(4-sulfobutyl)-4( 1H) -pyridylidene]rhodanine, sodium saltXII Anhydro-3-ethyl-9-methyl-3-(3-sulfobutyl)thiacarbocyanine hydroxideIt will be understood that cyanine dye salts such as above Dye Nos. I,II, III and V include not only the specified iodide and bromide salts,but also the chloride, sulfamate, thiocyanate, perchlorate,ptoluenesulfonate, methyl sulfate, etc. salts. Also, Dye N0. XI includesany of the alkali metal salts such as lithium, potassium, etc.

In preparing the novel dispersions of the invention, the weightproportions of the water-soluble liquid (which is a non-solvent for thedyes) to dye can vary over a wide range, such as from about :5 to 100150, but preferably from about 100:10 to 100240, respectively. Liquidswhich are dye solvents are advantageously used in weight proportions ofabout 5 to 20 parts solvent per each part by weight of dye.

Those dispersions of the invention containing a binder such as gelatincan vary widely in the proportions of dye to gelatin, but the bestresults for sensitizing purposes are obtained with compositions whereinthe dye varies from 20 to 40%, based on the total weight of dye plusbinder. For spectrally sensitizing photographic silver halide emulsions,the dispersions of the dyes can also contain two or more dyes in eachdispersion or dispersions containing a single dye can also be used incombinations of two or more such dispersions. Generally, theconcentration of dye incorporated into the emulsions by the method ofthe invention for optimum sensitivity varies depending on the dye andemulsion about from 0.20 to 4.0 grams of dye per mole of silver halidein the emulsion. The dye dispersions of the invention can be readilyincorporated into the emulsions by any suitable method such as mixing,mechanical blending, etc.

Compositions of the invention consisting essentially of organic liquidand dye can be added directly to liquid photographic silver halideemulsions to obtain good spectral sensitization. If desired, thecomposition of the invention can be dispersed in a hydrophilic colloid.The dispersion of dye-organic liquid in hydrophilic colloid can be usedin liquid or solid form to sensitize liquid silver halide emulsions. Thehydrophilic colloid used with the dye-organic liquid can be any colloidwhich is compatible with the photographic emulsions, such as any of thehydrophilic colloids referred to below. Gelatin is especially useful.The colloid is preferably free from silver halide, or, the mixturecomprises a substantial amount of dye which is unadsorbed on any silverhalide present in the colloid.

This invention is useful in spectrally sensitizing any liquidphotographic silver halide emulsion. The light sensitive silver halidecan be dispersed in any hydrophilic colloid (binder) that issatisfactory for dispersing silver halides, for example, gelatin,albumin, agar-agar, gum arabic, alginic acid, polyvinyl alcohol,polyvinyl pyrrolidone, cellulose ethers, partially hydrolyzed celluloseacetate, and the like. The hydrophilic colloid can also containdispersed polymerized vinyl compounds, such as those disclosed in U.S.Pats. 3,142,568; 3,193,386; 3,062,674 and 3,220,844 and include thewater insoluble polymers of alkyl acrylates and methacrylates, acrylicacid, sulfoalkyl acrylates or methacrylates and the like.

While the examples herein are illustrated with silver bromoiodideemulsions, it will be apparent that other silver halide emulsions suchas silver chloride, silver bromide, silver chlorobromide, silverchlorobromoiodide, etc. can also be efliciently sensitized in likemanner with the novel dye dispersions of the invention.

The emulsions prepared in accordance with the invention may be coated onany suitable photographic support such as cellulose acetate, celluloseacetate butyrate, polyesters such as poly(ethylene terephthalate),polyethylene,

polypropylene, paper, glass, and the like, to produce spectrallysensitized photographic elements.

The photographic emulsions prepared in accordance with the novel methodof this invention may contain such addenda as chemical sensitizers,e.g., sulfur sensitizers (e.g., allyl thiocarbamate, thiourea,allylisothiocyanate, cystine, etc.), various gold compounds (e.g.,potassium chloroaurate, auric trichloride, etc. (see Baldsiefen, U.S.Pat. No. 2,540,085, issued Feb. 6, 1951; Damschroder, U.S. Pat. No.2,597,856, issued May 27, 1952 and Yutzy et a1. U.S. Pat. No. 2,597,915,issued May 27, 1952), various palladium compounds such as palladiumchloride (Baldsiefen, U.S. Pat. No. 2,540,086, issued Feb. 6, 1951),potassium chloropalladate (Stauifer et al., U.S. Pat. No. 2,598,079,issued May 27, 1952), etc., or mixtures of such sensitizers,antifoggants such as ammonium chloroplatinate (Trivelli et al., U.S.Pat. No. 2,566,245, issued Aug. 28, 1951), ammonium chloroplatinite(Trivelli et al., U.S. Pat. No. 2,566,263, issued Aug. 28, 1951),benzotriazole, nitrobenzirnidazole, S-nitroimidazole, benzidine,mercaptans, etc. (see Mees-The Theory of the Photographic Process,MacMillan Pub., 1942, page 460), or mixtures thereof. The silver halideemulsions of the invention can be hardened with any suitable hardener,including aldehyde hardeners such as formaldehyde, and mucochloric acid,aziridine hardeners, hardeners which are derivatives of dioxane,oxypolysaccharides such as oxy starch or oxy plant gums, and the like.The emulsion layers can also contain additional additives, particularlythose known to be beneficial in photographic emulsions, including, forexample, lubricating materials, stabilizers, speed increasing materials,absorbing dyes, plasticizers, and the like. These photographic emulsionscan also contain in some cases additional spectral sensitizing dyes.Furthermore, these emulsions can contain color forming couplers or canbe developed in solutions containing couplers or other color generatingmaterials. Among the useful color formers are the monomeric andpolymeric color formers, e.g., pyrazolone color formers, as well asphenolic, heterocyclic and open chain couplers having a reactivemethylene group. The color forming couplers can be incorporated into thephotographic silver halide emulsion using any suitable technique, e.g.,techniques of the type shown in Jelley et al. U.S. Pat. 2,322,027,issued June 15, 1943, Fierke et al. U.S. Pat. 2,801,171, issued July 30,1957, Fisher U.S. Pats. 1,055,155 and 1,102,028, issued Mar. 4, 1913 andJune 30, 1914, respectively, and Wilmanns U.S. Pat. 2,186,849, issuedJan. 9, 1940. They can also be developed using incorporated developerssuch as polyhydroxybenzenes, aminophenols, 3 pyrazolidones, and thelike.

The following examples are included for a further understanding of thisinvention.

EXAMPLE 1 1.350 g. of Dye No. I are milled for 6 hours in a ballmillwith 6 cc. of methylglycol to give a dye dispersion wherein the dyeparticles have an average diameter less than about 1 micron. To thisdispersion 18 g. of a gelatin solution are then added. The mixture ishomogenized in a ball-mill for 15 minutes. The mixture is then airdried, formed into flakes so as to be readily bottled and stored at roomtemperature in a brown glass bottle. A suitable sample of the mixture isused to determine the dye content of the mixture. In the presentexample, the dye concentration is 31.5% by weight.

EXAMPLES 2-11 The procedure described in above Example 1 is repeatedwith each of the other dyes listed in Table 1 above, namely, Dye Nos. IIto XI to give the corresponding dye dispersions in the concentrationslisted in the following table.

TAB LE 2 Gone. 01-- Gelatin solution Dye cone. Methyl- Total Gone. infinal Dye glycol soln. gelatin mix (wt. (grams) (co (grams) (grams)percent) EXAMPLE 12 A negative gelatino silver bromoiodide emulsion isdigested to optimum sensitivity with a labile sulfur compound and asoluble gold salt. It is then divided into two portions (a) and (b) andeach portion is optically sensiper 10 moles of silver halide in theemulsion. In portion (a), the dye mixture is added in solution inconventional solvents such as methanol. In portion (b), the dye mixtureis milled with methyl glycol and dispersed in gelatin as described inabove Example 1 and the resulting dispersion is then added to theemulsion.

Each of these two emulsions is kept at 40 C. for 20 minutes and theneach is coated onto a separate cellulose acetate film support. Thecoated samples are sensitometrically tested by successive exposures ofeach sample to white light and through Wratten Filters No. 25 whichtransmits light at wavelengths longer than about 590 nm., No. 47 whichtransmits light in the region of about from 350 to 530 nm., and No. 58which transmits light in the region of about from 470 to 615 nm.,followed by development for about 6 minutes at room temperature in KodakD-19 developer which has the following composition:

G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite (anhydrous) 90.0Hydroquinone 8.0 Sodium carbonate (monohydrate) 52.5 Potassium bromide5.0

Water to make 1.0 liter.

then fixed, washed and dried. The resulting speed values for theemulsions sensitized by processes (a) and (b) are shown to be identicalby the test procedure of this example. Similar good results ofsensitization are likewise obtained when the dispersion of the dyes inmethylglycol is used directly, without binder or drying, in the silverhalide emulsion.

EXAMPLE 13 The photographic tests carried out in this example aresimilar to those described in above Example 12, except that thepreparation of the milled dyes dispersed in gelatin were made 3 monthsbefore. The sensitometric results, which are identical with thosedescribed in the preceding example, show the good keeping properties ofthe dye dispersions of the invention.

EXAMPLE 14 A negative silver halide emulsion similar to that describedin above Example 12 is optically sensitized with the dye mixture:

G. Dye No. IV 1.00 Dye No. V 1.13

Dye N0. VI 1.13

per 10 moles of silver halide in the emulsion, in accordance withmethods (a) and (b) described in Example 12. The tests show that thespeeds of the emulsions optically sensitized by methods (a) and (b) inthis example are identical to white light, to light transmitted throughWratten Filter No. 47 and to light transmitted through Wratten FilterNo. 58.

EXAMPLE 15 A mixture of Dye Nos. I, II an III, in the proportions givenin above Example 12, is milled with 10 cc. of methyl glycol until thedye particles have an average diameter less than about 1 micron. Theresulting dye paste is dispersed in 12 g. of a 15% aqueous gelatinsolution, dried and then used to sensitize a photographic silver halideemulsion, as described in Example 12. The sensitivity of this emulsionis substantially the same as that of the emulsion prepared in Example 12by method (a), except that the speed loss in white light as compared tothe control is 0.08 log E.

EXAMPLE 16 This example is identical with that of Example 15, exceptthat the mixture of dyes is milled with 12 cc. of glycerol and taken upwith 20 g. of a 10% aqueous gelatin solution. The sensitometric resultsof this example are identical with those of above Example 15.

EXAMPLE 17 The mixture of dyes described in Example 14 is milled with 10cc. of methylglycol, taken up with 30 g. of 10% gelatin solution anddried. The dry mixture is used for optically sensitizing a photographicemulsion by the method described in Example 12.

The emulsion sensitized with the solid mixture (method b) shows a speedloss of 0.10 log E as compared to the control (method a), in whitelight.

EXAMPLE 18 This example and results thereof are identical with those ofExample 17, except that the dye mixture is milled with 15 cc. ofglycerin.

In Examples 15, 16, 17 and 18, the small loss in sensitivity appears toresult from loss of dyes when the mixtures are recovered from theball-mills.

EXAMPLE 19 500 mg. of Dye II are milled for 24 hours in a ballmill inthe presence of cc. of methanol. Less than 5% by Weight of the totalamount of dye is dissolved in methanol. 50 cc. of a aqueous gelatinsolution are then added and the mixture is effected in the same ballmillat 40 C. for 2 hours. This mixture is coated on unsubbed poly(ethyleneterephthalate) support, in the form of a film having a thickness of30,11. to 40 After drying, the film which adheres to the support due tothe effect of electrostatic charges is readily stripped from the base.It is broken into flakes by being passed through a grate under theaction of compressed air. It is then readily weighed, titrated andstored. The mixture, which contains about 8% by weight of dye, is usedto spectrally sensitize an emulsion as described in Example 12. Thespectral sensitometric results obtained, as in Example 12, are identicalwith those obtained by conventional spectral sensitization methods(i.e., when the dye is dissolved in an aqueous solution of methanol andadded to the emulsion).

EXAMPLE 20 The procedure of Example 19 is repeated except that the 5 cc.of methanol are replaced with 5 cc. of a 90:10 methanol-glycerinmixture. Identical sensitometric results are obtained.

EXAMPLES 2 l-26 The procedures of Examples 19 and 20 are repeated,except that in each Example Dye II is replaced with 500 mg. of Dyes I,III and XII. The sensitometric results, obtained as in Example 12, areidentical to those ob tained when the dyes are added to the sameemulsion from methanol solutions.

It is well known in the photographic art that effective spectralsensitization of light sensitive silver halide depends on the dyes beingadsorbed to the silver halide grains. See Mees and James, The Theory ofthe Photographic Process, 3d. edition, published by the MacMillanCompany, 1966, page 236, column 2. One skilled in the photographic artwould not expect particles of spectral sensitizing dyes, which areinsoluble in aqueous systems, to migrate through a hydrophilic colloidand become efiiciently adsorbed to the silver halide.

It will be apparent from all the foregoing that any other of the dyesmentioned in Table 1 above, as well as still other known cyaninesensitizing dyes that are Waterinsoluble, can be substituted in theprocedures of the above examples to give generally similar usefulresults. Also, any other of the mentioned water-soluble dihydroxyalkanesor lower monoalkyl ether derivatives thereof which are non-solvents forthe sensitizing dyes, glycerol, monoacetin, ethylene glycol,methylglycol, ethyl glycol ether, propyl glycol ether, butyl glycolether, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol,2,3-butylene glycol, isobutylene glycol, 2-methyl-2,3-butanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1,4-pentanediol,2,3-pentanediol, 1,5-pentanediol, etc. can be substituted for themethylglycol and glycerol components in the procedures of the aboveexamples with similar resulting ad- Vantage.

The invention has been described in detail with particular reference topreferred embodiments thereof, but, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention described hereinabove and in the appended claims.

We claimzi II. A process for spectrally sensitizing photographic silverhalide which comprises: dispersing a substantially water-insolublephotographic spectral sensitizing dye in a water-soluble organic liquidwhich is a non-solvent for said dye; and, incorporating said dispersioninto a liquid photographic silver halide emulsion, said organic liquidhaving the following formula:

wherein R represents a member selected from the group consisting of ahydrogen atom and an alkyl group containing from 1 to 4 carbon atoms; Rrepresents a member selected from the group consisting of a hydrogenatom and a methyl group; R represents a member selected from the groupconsisting of a hydrogen atom, an alkyl group containing from 1 to 3carbon atoms, a hydroxy-alkyl group of from 1 to 3 carbon atoms and anacetoxymethyl group; and, R represents a divalent alkylene groupcontaining from '1 to 4 carbon atoms, the sum of the carbon atoms insaid R R and R being from 1 to 4.

2. The process for spectrally sensitizing silver halide which comprises:dispersing a substantially water-insoluble photographic spectralsensitizing dye in an organic liquid selected from the group consistingof glycerol, monoacetin, ethylene glycol, methylglycol, ethyl glycolether, propyl glycol ether, butyl glycol ether, 1,3-propylene glycol,1,3-butylene glycol, 1,4-butylene glycol, 2,3- butylene glycol,isobutylene glycol, 2-methyl-2,3-butanediol, 3-methyl-1,3butanediol,1,2-pentanediol, 1,4-pentanediol, 2,3-pentanediol, and 1,5-pentanediol;and, incorporating said dispersion into a liquid photographic silverhalide emulsion to spectrally sensitize the silver halide.

in accordance with claim 1 wherein the dispersion of dye in organicliquid is mixed with an aqueous solution of a hydrophilic colloid toform a homogenous mixture and said mixture is incorporated into thelight-sensitive silver halide emulsion.

4. The process for spectrally sensitizing silver halide in accordancewtih claim 3 wherein said aqueous mixture of dye, organic liquid andhydrophilic colloid is dried prior to incorporation into saidlight-sensitive silver halide emulsion.

5. A process for spectrally sensitizing photographic silver halide whichcomprises: dispersing in methylglycol a photographic spectralsensitizing dye selected from the group consisting of1'ethyl-2-methylthia-4'-cyanine salt;

3,3-diethyl-9-methylselenacarbocyanine salt;

3-ethyl-5-[ (3-ethyl-2 3H) -benzothiazlylidene)isopropylidene]-2-thio-2,4-oxazolidinedione;

9-ethyl-3,3-di( fi-methoxyethyD-S ,5 -diphenyloxacarbocyanine salt;

anhydro-S,5,6, 6-tetrachloro-1,l'-diethyl-3,3'-di(3-sulfo==butyl)-benzimidazolocarbocyanine hydroxide;

-[ (3-ethyl-2 3H) -n'aphtho [2,t1 oxazolylidene) ethylene]3-n-heptyl-1-phenyl-2-thiohydantoin;

5- 3-ethyl-2 3H -benzoxazolylidene) -3-phenylrhodanine;

anhydro-S,5-dichloro-3,9-diethyl-3-(3-sulfobutyl)thiacarbocyaninehydroxide;

5- [di 3-ethyl-2(1H)-naphtho[1,2]thiazolylidene)isopropylene]-1,3-di(,B-methoxyethyl)barbituric acid; and

3-ethyl-5- l- (4-sulfobutyl) -4( 1H) -pyridylidene] rhodanine, sodiumsalt;

and incorporating said dispersion into an aqueous gelatin photographicsilver halide emulsion to epectcally sensitize the silver halideJ 6. Theprocess in accordance with claim 5 wherein the dispersion of dye inmethylglycol is mixed with an aqueous solution of gelatin to form ahomogeneous mixture, and said mixture is incorporated into saidphotographic silver halide emulsion.

7. The process for spectrally sensitizing silver halide in accordancewith claim 5 wherein said mixture is dried prior to incorporation intothe photographic silver halide emulsion.

8. A process for spectrally sensitizing photographic silver halide whichcomprises: dispersing in glycerol a photographic spectral sensitizingdye selected from the group consisting of1'-ethyl-2-methylthia-4'-cyanine salt;

3,3'-diethyl-9-methylselenacarbocyanine salt;

1,1'-diethyl-2,2'-cyanine salt;

3-ethyl-5- 3-ethyl-2 3H) -'benzothiazolylidene) -isopropylidene]-2-thio-2,4-oxazolidinedione;

9-ethyl-3,3 '-di( B-methoxyethyl) -5 ,5 '-diphenyloxacarbocyanine salt;

anhydro-5,5','6,6'-tetrachloro-l,1'-diethyl-3,3'-di(3-sulfobutyl)benzimidazolocarbocyaninehydroxide;

5- [3-ethyl-2 3H)naphtho [2, l oxazolylidene) ethylene] -3-n-heptyl-il-phenyl-2-thiohydantoin;

5- 3-ethyl-2( 3 H) -b enzoxazolylidene) -3-phenylrhodanine;

anhydro-S ,5 '-dichloro-3,9-diethyl-3-(3-sulfobutyl)thiacarbocyaninehydroxide;

5- [di 3-ethyl-2( 1H )-naphtho[ 1,2] thiazolylidene)isopropylene]-1,3-di(fl-methoxyethyl)barbituric acid; and

3-ethyl-5- [.l- (4-sulfobutyl -4( 1H) -pyridylidene] rhodanine, sodiumsalt;

and, incorporating said dispersion into an aqueous gelatin photographicsilver halide emulsion.

9. A process for spectrally sensitizing photographic silver halide whichcomprises: dispersing a substantially water-insoluble photographicspectral sensitizing dye in a water-soluble organic liquid mixturewithout dissolving the dye, said organic liquid mixture comprising aboutto parts by weight of an organic liquid selected from the groupconsisting of an alcohol having from 1 to 4 carbon atoms, acetone anddimethylformamide, and, about 20 to 5 parts by weight of an organicliquid having the following formula:

wherein R represents a member selected from the group consisting of ahydrogen atom and an alkyl group containing from 1 to 4 carbon atoms; Rrepresents a member selected from the group consisting of a hydrogenatom and a methyl group; R represents a member selected from the groupconsisting of a hydrogen atom, an alkyl group containing from 1 to 3carbon atoms, a hydroxyalkyl group of from 1 to 3 carbon atoms and anacetoxymethyl group; and, R represents a divalent alkylene groupcontaining from 1 to 4 carbon atoms, the sum of the carbon atoms in saidR R and R being from 1 to 4; and, incorporating said dispersion into aliquid photographic silver halide emulsion to spectrally sensitize thesilver halide.

10. A process as defined in claim 9 wherein said organic liquid mixturecomprises about 80 to 95 parts by weight methanol and about 20 to 5parts by weight glycerol.

11. A process for spectrally sensitizing silver halide which comprises:dispersing, in about 5 cc. of an organic liquid mixture comprising 9parts by weight methanol and 1 part by weight glycerol, about .5 gram of3-ethyl-5-[(3- ethyl 2(3H) benzothiazolylidene)isopropylidene] 2-thio-2,4-oxazolidinedione.

12. A mixture comprising a hydrophilic colloid and a dispersion of aphotographic spectral sensitizing dye in a water-soluble organic liquidin which the dye is insoluble, said organic liquid having the followingformula:

wherein R represents a member selected from the group consisting of ahydrogen atom and an alkyl group containing from 1 to 4 carbon atoms; Rrepresents a member selected from the group consisting of a hydrogenatom and a methyl group; R represents a member selected from the groupconsisting of a hydrogen atom, an alkyl group containing from 1 to 3carbon atoms, a hydroxyalkyl group of from 1 to 3 carbon atoms and anacetoxymethyl group; and R represents a divalent alkylene groupcontaining from 1 to 4 carbon atoms, the sum of the carbon atoms in saidR R and R being from 1 to 4.

13. A mixture comprising a hydrophilic colloid and a dispersion asdefined in claim 12 wherein said organic liquid is selected from thegroup consisting of glycerol, monoacetin, ethylene glycol, methylglycol,ethyl glycol ether propyl glycol ether, butyl glycol ether,1,3-propylene glycol, 1,3-butylene glycol, 1,4 butylene glycol,2,3-butylene glycol, isobutylene glycol, 2-methyl-2,3-butanediol, 3-methyl 1,3-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,3-pentanedioland 1,5-pentanediol.

References Cited UNITED STATES PATENTS 3,469,987 9/1969 Owens ct a1.96l32 I. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R.

